A randomized clinical trial comparing the efficacy of lidocaine administered intravenously, intranasally or as infraorbital nerve block in dogs undergoing rostral rhinosocopy.

OBJECTIVE:To compare the efficacy of lidocaine administered intravenously, intranasally or as an infraorbital nerve block in dogs undergoing rostral rhinoscopy. STUDY DESIGN:Randomized clinical trial. ANIMALS:A total of 43 client-owned dogs. METHODS:After premedication with medetomidine 0.01 mg kg-1 and methadone 0.2 mg kg-1 intramuscularly, anaesthesia was induced with propofol and maintained with isoflurane in oxygen. Dogs were randomly allocated to receive 2 mg kg-1 of 2% lidocaine as a bilateral infraorbital nerve block (INB) via the caudal intraoral approach, via bilateral topical intranasal administration (TIA) or as an intravenous bolus (IVB). At 5 minutes following lidocaine administration, responses to rhinoscopy (RR) and biopsies (RB) were evaluated using a simple scoring system (0: no reaction; 1: reaction). Response to the rhinoscopy in the recovery period (RE) was recorded. Recovery quality was scored using a simple descriptive score. Heart rate, respiratory rate and noninvasive arterial blood pressure were recorded. Intravenous (IV) fentanyl 0.001 mg kg-1 was administered if an increase > 20% in any variable occurred. Gross movement was attenuated using propofol 0.5 mg kg-1 IV. Scores were analysed using the Chi-square test with Monte Carlo method. Cardiorespiratory changes among and overtime between groups were compared using one-way anova and one-way anova for repeated measures, respectively, or the correspondent non-parametric tests; p < 0.05. RESULT:Of the 43 dogs, 42 completed the study. No statistically significant differences were detected in either physical reactions or changes in cardiorespiratory variables for RR, RB, RE or recovery quality, although RB tended to be higher in group TIA (7/10 versus 1/10 INB and 3/13 IVB).Various cardiorespiratory variables changed overtime within groups. CONCLUSIONS AND CLINICAL RELEVANCE:In dogs, all three investigated techniques attenuated responses during rostral rhinoscopy in dogs, although INB and IVB were more efficacious when biopsies were taken.